Source: dropbear
Version: 2018.76-1
Severity: normal
Tags: patch
User: [email protected]
Usertags: origin-kali kali-patch
When dropbear is used in a very restricted environment (such as in a
initrd), the default user shell is often also very restricted
and doesn't take care of setting the PATH so the user ends up
with the PATH set by dropbear. Unfortunately, dropbear always
sets "/usr/bin:/bin" as default PATH even for the root user
which should have /usr/sbin and /sbin too.
For a concrete instance of this problem, see the "Remote Unlocking"
section in this tutorial:
https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/
It speaks of a bug in the initramfs script because it's written "blkid"
instead of "/sbin/blkid"... this is just because the scripts from the
initramfs do not expect to have a PATH without the sbin directories and
because dropbear is not setting the PATH appropriately for the root user.
I'm thus suggesting to use the attached patch to fix this misbehaviour (I
did not test it, but it's easy enough). It might seem anecdotic but
multiple Kali users have been bitten by this.
(This bug report is copied to the upstream author Matt Johnston
<[email protected]> in the hope that he will consider this bugreport and
apply the patch)
-- System Information:
Debian Release: buster/sid
APT prefers oldoldstable
APT policy: (500, 'oldoldstable'), (500, 'unstable'), (500, 'testing'), (500,
'stable'), (500, 'oldstable'), (1, 'experimental')
Architecture: amd64 (x86_64)
Foreign Architectures: i386
Kernel: Linux 4.16.0-2-amd64 (SMP w/4 CPU cores)
Locale: LANG=fr_FR.UTF-8, LC_CTYPE=fr_FR.UTF-8 (charmap=UTF-8),
LANGUAGE=fr_FR.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled
--
Raphaël Hertzog ◈ Debian Developer
Support Debian LTS: https://www.freexian.com/services/debian-lts.html
Learn to master Debian: https://debian-handbook.info/get/
--- a/default_options.h
+++ b/default_options.h
@@ -291,5 +291,6 @@ be overridden at runtime with -I. 0 disa
/* The default path. This will often get replaced by the shell */
#define DEFAULT_PATH "/usr/bin:/bin"
+#define DEFAULT_ROOT_PATH "/usr/sbin:/usr/bin:/sbin:/bin"
#endif /* DROPBEAR_DEFAULT_OPTIONS_H_ */
--- a/svr-chansession.c
+++ b/svr-chansession.c
@@ -961,7 +961,11 @@ static void execchild(const void *user_d
addnewvar("LOGNAME", ses.authstate.pw_name);
addnewvar("HOME", ses.authstate.pw_dir);
addnewvar("SHELL", get_user_shell());
- addnewvar("PATH", DEFAULT_PATH);
+ if (getuid() == 0) {
+ addnewvar("PATH", DEFAULT_ROOT_PATH);
+ } else {
+ addnewvar("PATH", DEFAULT_PATH);
+ }
if (chansess->term != NULL) {
addnewvar("TERM", chansess->term);
}
